(1) Field of the Invention
The present invention relates to a novel compound having a photochromic action, a composition comprising this compound, and a use thereof. More particularly, the present invention relates to a novel compound which is colored from the colorless state under irradiation of an ultraviolet ray-containing light such as sunlight or a light of a mercury lamp, this change is reversible and the color fading speed is high, a composition comprising this novel compound and a use thereof.
(2) Description of the Related Art
The photochromism is the phenomenon which has attracted attention in these several years, and this phenomenon is a reversible phenomenon in which when a certain compound is irradiated with an ultraviolet ray-containing light such as sunlight or a light of a mercury lamp, the color of the compound is promptly changed and when the irradiation is stopped and the compound is placed in the dark place, the original color is manifested again. The compound having this property is called "photochromic compound", and various photochromic compound have been synthesized. However, a special common structure is not found among these compounds.
The specification of U.S. Pat. No. 4,826,977 discloses spiroadamantane compounds represented by the following formulae (A) and (B): ##STR4##
The compound (A) is poor in the practical utility because the coloration is caused only at temperatures lower than 10.degree. C. The compound (B) shows a photochromic characteristic at temperatures close to normal temperature (10.degree. to 40.degree. C.), and it is known that the compound is changed to a yellow or orange color from the colorless state. However, in the spiroadamantane compound (B), the colored form is relatively stable and the color fading speed at the ambient temperature is not so high, presumably because of the presence of the bulky adamantylidene group. Therefore, when this compound is used for a photochromic lens, even by stopping irradiation with sunlight, a long time is required for restoring the lens to the colorless form from the colored form.